# std::ranges::views::values, std::ranges::values_view

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< cpp‎ | ranges

Defined in header `<ranges>` |  |
template< class R > using values_view = ranges::elements_view<R, 1>; | (1) | (since C++20)
namespace views { inline constexpr auto values = ranges::elements<1>; } | (2) | (since C++20)

Takes a `view` of tuple-like values (e.g. std::tuple or std::pair), and produces a view with a value-type of the second element of the adapted view's value-type.

1) An alias for ranges::elements_view<R, 1>.
2) RangeAdaptorObject (and also RangeAdaptorClosureObject). The expression views::values(e) is expression-equivalent to values_view<views::all_t<decltype((e))>>{e} for any suitable subexpression e.

### Notes

values_view can be useful for extracting values from associative containers, e.g.

    std::map<int, std::string> map{{1, "alpha"}, {2, "beta"}};
    for (auto const& value : std::views::values(map))
        std::cout << value << ' ';
    // prints: alpha beta

### Example

Run this code

    #include <iostream>
    #include <map>
    #include <ranges>

    int main()
    {
        const auto list = {std::pair{1, 11.1}, {2, 22.2}, {3, 33.3}};
        std::cout << "pair::second values in the list: ";
        for (double value : list | std::views::values)
            std::cout << value << ' ';

        std::map<char, int> map{{'A', 1}, {'B', 2}, {'C', 3}, {'D', 4}, {'E', 5}};
        auto odd = [](int x) { return 0 != (x & 1); };
        std::cout << "\nodd values in the map: ";
        for (int value : map | std::views::values | std::views::filter(odd))
            std::cout << value << ' ';
        std::cout << '\n';
    }

Output:

    pair::second values in the list: 11.1 22.2 33.3
    odd values in the map: 1 3 5

### Defect reports

The following behavior-changing defect reports were applied retroactively to previously published C++ standards.

DR | Applied to | Behavior as published | Correct behavior
--- | --- | --- | ---
LWG 3563 | C++20 | `keys_view` is unable to participate in CTAD due to its use of views::all_t | views::all_t removed

### See also

ranges::keys_viewviews::keys (C++20) | takes a `view` consisting of pair-like values and produces a `view` of the first elements of each pair (class template) (range adaptor object)
ranges::elements_viewviews::elements (C++20) | takes a `view` consisting of `tuple-like` values and a number N and produces a `view` of Nth element of each tuple (class template) (range adaptor object)
slice | BLAS-like slice of a valarray: starting index, length, stride (class)

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